Typically there is only one elevator per elevator shaft. In an attempt to save space and improve waiting time, some cableless elevators have been described, such as in U.S. Pat. Nos. 5,501,295, 4,051,923 and 3,658,155. These elevators can travel vertically and horizontally, but are not designed to travel along a curved track or a track that is neither vertical nor horizontal because the elevator cab will not stay in a vertical position.
In current elevator systems, such as traction or machine room-less elevators, hoist cables above an elevator cab are used for pulling the cab up or down in a elevator shaft. The hoist cables are firmly connected to the elevator cab at one end and counter weights at the other. Machine sheave is turning to bring the elevator up and down. The disadvantages for these elevators are obvious, and include the requirement for a machine room or space in the shaft to locate the machineries, maintenance of the cables due to wear and tear, and tripping hazard due to re-leveling as a result of cables stretching or weight changing when passengers enter or exit the elevator. The design of such elevators is limited, and typically involves up and down movement of a single elevator cab in a straight vertical elevator shaft. Furthermore, these elevators cannot fit into elevator shaft that are built to be used for hydraulic elevators because of the space limitation.
For hydraulic elevators, they suffer from the disadvantages of slow speed, noisy operation and a relatively low height limit. The hydraulic elevators may also pose environmental hazard when there is leakage of the hydraulic fluid. Typically, the elevator cab is connected directly or indirectly through hoist cables with a hydraulic piston. When the piston goes up and down, so does the elevator. There are currently some devices to achieve ACO (ascending cab over speed protection) and UCM (unintended cab movement protection) protection like electric stop valve and piston brake. An electric stop valve stops the pump from providing pressure so as to stop the elevator. A piston brake clamps on the piston to stop the elevator.
Current options for stopping the elevator cabs during an emergency includes:                1) Rope gripper, which clamps on the hoist cables to stop the elevator.        2) Sheave brake, which clamps on the traction sheave to stop the elevator.        3) Emergency Brake on motor, which clamps on the motor shaft or pulley to stop the elevator.        
Most of the current solutions will work on new elevator systems but may be difficult to be adapted to older and existing elevators. However, all the methods mentioned above only indirectly stop the elevator cab, and they suffer from substantial shortcomings. For example, if the hoist cable breaks, the elevator will fall, and all of the above-mentioned emergency brake systems will be useless. Also, they all require the elevator controller to have circuitries and programs in order for them to function.
There is significant need for better designed elevators and ways to overcome the problems with current traction, machine room-less and hydraulic elevators. The present invention serves to address these problems.